America Has a Manure Problem, and the Miracle Solution Being Touted Isn’t All that It Seems
(The Guardian) … Manure from animal agriculture is a primary source of nitrogen and phosphorus pollution in US waterways, making water undrinkable and causing algae blooms that kill wildlife. Manure is also a significant source of greenhouse gas emissions on livestock farms – and much of its impact depends, specifically, on how it’s managed and stored. Twelve per cent of all greenhouse gas emissions from the US agricultural sector come from what the EPA calls “manure management”.
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In the past five years, there has been a surge of partnerships between animal farms and natural gas companies promoting the use of anaerobic digesters, which turn manure into a form of energy called biogas. The EPA has identified more than 8,000 dairy and hog operations as prime candidates for future on-farm digesters. Amid talks at Cop26, the Biden administration pointed to an expanding biogas industry as crucial to its methane emissions action plan.
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If properly managed, digesters could help polluting CAFOs get their manure under control. And good manure management – that is, following the best practices for collecting, storing and applying manure as a fertilizer – is critical for curbing pollution
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Anaerobic digesters use bacteria to break down organic matter in an oxygen-free environment, like a sealed reactor or lagoon. Gases such as carbon dioxide, water vapor and methane are then separated from the liquid and solid digested waste, and the system can then process the biomethane so it can be used as natural gas.
That natural gas can be used as an on-farm power source or sold to a gas treatment system or local utility. What’s left over – the solid and liquid digested waste – is then stored until it can be applied to cropland, or sold to other farms or garden stores as livestock bedding or potting mix.
This storage solution could help on industrial pig farms, where manure is typically stored in pits or “lagoons”. Lagoons especially can become ticking ecological timebombs when a storm comes through. Heavy rainfall can lead to manure overflowing into nearby lakes and even well water.
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Critics warn that manure digesters shouldn’t be used to justify the expansion of factory farming, which is already a huge contributor of greenhouse gas emissions globally, as well as local air and water pollution. READ MORE
